Thermosetting coating compositions



David W. Glaser, St. Paul, Minn., assignor to General Mills, Inc., acorporation of'Delaware N Drawing. Application March 8, 1956 Serial No.570,209

9 Claims. (Cl. 26047) This invention relates to novel protectivecoatings. More specifically, this invention relates to novelcompositions of epoxy resinous materials and certain ali-.

States Patent O phatic diamines and the method of curing thesecompositions.

Various amines and diamines have been used to cure epoxy resins.Diamines are generally preferred because they produce cross-linkedproductshaving desirable characteristics such as chemical resistivity,high heat distortion temperatures, and so forth.

It has now been discovered that aliphatic fatty diamines having arelative high iodine number may be mixed with epoxy resinouscompositions in such a manner that a unique surface coating is obtained.One unique feature of this surface coating is that it contains 100%solids. In other words no solvent or carrier is required, and as acoating it is self-contained i.e.,

the curing and hardening is a function of the aliphatic fatty diamineand epoxy resinous compositions. There is no need for oxygen penetrationof the coating as in the case of protective coatings employing dryingoilsor other constituents that harden upon exposure to the air. There isno need for contact with the atmosphere in order to permit theevaporation of solvent or other carrier. Graphic proof of the uniquenessof this composition as a surface coating is that it will cure and hardenin thick films which afford protective coatings of maximum durabilityand corrosion resistance. Previously the preparation of smooth filmsover about 3 mils thick in one application have been for the most part"unsatisfactory. By employing the compositions hereinafter set forth itis possible to achieve a film thickness 'as high as 25 mils and higher.

Aliphatic diamines envisioned by this inventionhave the structuralformula 225 to 350. The iodine number is the number of grams of halogenexpressed as halogen absorbed by a 100 gram sample. The amine number isan expression of the number of milligrams of potassium hydroxideequivalent to the amine groups in a one gram sample.

These, diaminesmay be prepared by the; addition of acrylonitrile tofatty amines and subsequently reducing the nitrile formed to thecorresponding diamine. This reaction is outlined below.

where R is as shown above.

The fatty amine employed in the above reaction can be prepared by thereaction of ammonia with fatty acids to form the fatty nitrile andsubsequent reduction of the nitrile to the corresponding fatty amine.The procedures and conditions employed in the above reactions arewell-known and practiced commercially.

The fatty acids used to prepare the, fatty amine are generally derivedfrom naturally occurring vegetable and animal fats and oils and willhave 8 to 22 carbon atoms with a preponderance of the acids containing18 carbon atoms. Illustrative vegetable oils are soybean oil, cottonseedoil, coconut oil, palm oil, tung oil, castor oil etc. Fats and oilsderived from animals are exemplified by tallow and greases. The fattyacids derived from each of these fats and oils are complex mixtures thatare not easily separated into the individual acids. For this reason thefatty acids employed to prepare the fatty amines will generally be amixture. One method of classifying acid mixtures derived from thevarious oils is by their iodine number. As stated above, the iodinenumber is the numberof grams of halogen expressed as iodine which willreact with a gram sample. Or in other words as pertinent to fatty acidsit is an indication of the amount of unsaturated fatty acids in themixture.

"Common unsaturated acids are oleic, eleostearic, dehydrated ricinoleic,linoleic, linolenic, and ricinoleic acid,

soybean oil, cottonseed oil, tung oil and other oils having a highiodine number or by separating the saturated fatty acids'from theunsaturated fatty acids by distillation or crystallization. In thisregard it is important to note that substantially all the double bondsor unsaturation of the fatty acid long-chained aliphatic radical shouldnot be disturbed during the preparation of the fatty nitrile, fattyamine and fatty diamine. Alternatively, suitable diamines may beobtained by separating diamines having a sufficiently high iodine numberfrom various other diamine mixtures which do not have a sufficientlyhigh unsaturation. This may be accomplished most easily by fractionalcrystallization. Such a separation is analogous to the Well-knownWinterizing of fats and oils.

The commercially available diamines of the above general type do nothave sufliciently high iodine numbers for the purposes of this inventionand a separation as described above was carried out to obtain diamineshaving an iodine number greater than 75. The exact reason for theinferiority of the lower iodine number diamines is not known but it hasdefinitely been observed that coatings in which such low iodine numberdiamines were used were speckled throughout with tiny areas in which thecoating was brittle and broke loose from the supporting surface.

The epoxy resins (glycidyl polyethers) employed in this invention arecomplex polymeric reaction products of polyhydric phenols withpolyfunctional halohydrins and/or glycerol dichlorohydrin. The productsthus obtained contain terminal epoxy groups. A large number of epoxyresins of this type are disclosed in Greenlee Patents 2,585,115 and2,589,245. Several of these resins are readily available to commercialproducts.

Typical polyhydric phenols useful in the preparation of epoxy resinsinclude resorcinol and various bisphenols resulting from thecondensation of phenol with aldehydes and ketones such as formaldehye,acetaldehyde, acetone, methyl ethyl ketone and the like. A typical epoxyresin is the reaction product of epichlorohydrin 3 4 and2,2-bis(p-hydroxy phenyl) propane (Bisphenol A), Therefore, manymodifications and variations of the the resin having the followingtheoretical structural forinvention as hereinbefore set forth may bemade without mula, departing from the spirit and scope thereof, andtherefore OH: OH CH: 0 can.HP.)a-..l@ t@ o cm tfl m oL+ ames.H.

\ (311: )a CH:

where n is 0 or an integer up to 10. Generally speaking, only suchlimitations should be imposed as are indicated n will be no greater than2 or 3 and is preferably 1 or in the appended claims. less. Havingdescribed my invention, I claim:

Epoxy resins may be characterized further by referl. Compositionssuitable as protective coatings comence to their epoxy equivalent, theepoxy equivalent of prising (a) an aliphatic diamine having an iodinenumpure epoxy resins being the mean molecular weight of her greater than75 and the structural formula the resin divided by the mean number ofepoxy radicals per molecule, or in any case the number of grams of wi-(0119M P Y equivalent I0 one mole of the P Y group in which R is analiphatic hydrocarbon radical having 9 gram-qulvalem of p P Y resinous 8to 22 carbon atoms and x is an integer from 1 to 4,

posltions havlrgg pp y equivalent of 140 to 1000 y and (b) a glycidylpolyether of 2,2-bis(p-hydroxy phenyl) be p y In thls inventiondePeflding upon the propane having an epoxy equivalent of 140 to 1,000.

Plication qesifed and conditions efnPloyed, however an 2. Thecomposition of claim 1 in which R is derived P Y equlvalency of 140 to350 is from a mixture of fatty acids having an iodine number Thefollowing examples illustrate working embodigreater than 110 d l h 200,

me Of this inventiofl- A11 T are expressed as 3. The composition ofclaim 1 in which x is 3.

P y Weight 4. Compositions suitable for protective coatings com- Example1 prising an aliphatic diamine having the structural for- 60 parts of anepoxy resin having an epoxy equivalency mula of approximately 180 andprepared by reacting Bisphenol R (CH2):NHI A and epichlorohydrin wasmixed with parts of a fatty aminopropylamine having an iodine number of95 and derived from the unsaturated fatty acids of soybean oil. Thismixture had a viscosity of C on the Gardner-Holdt scale when freshlymixed and a viscosity of H after standing 2 hours. Coatings of thiscomposition were only slightly tacky after curing at room tem peraturefor 1 day and were tack free after curing for 4 days at roomtemperature. Coatings of this composition 5 mils thick on glass panelshad a Sward hardness of 8 after curing at room temperature for 7 daysand a Sward hardness of 4 after being baked 15 minutes at 300 F. andcoatings on steel panels had an impact resistance after curing at roomtemperature greater than H 172 inch pounds. The same steel panels after118 hours 0 D in the Weather-O-Meter still had an impact resistance inWhlch R 15 an aliphatic lf f l'adlcal hall/m8 greater than 172 inchpounds. Coatings from the above 8 to 22 F 9 and I 15 all Integer from 110 4 composition remained hard after overnight immersion and hill/111gall lodme f greater than 75 and a in 20% NaOI-I and 37% H The generalappeary y polyether of (pv p v p p in which R is an aliphatichydrocarbon radical having 8 30 to 22 carbon atoms and x is an integerfrom 1 to 4 and having an iodine number greater than 75, said diaminebeing derived from a diamine mixture having an iodine number less than75 by fractional crystallization, and

a glycidyl polyether of 2,2-bis(p-hydroxy phenyl)pro- 35 pane having anepoxy equivalent from 140 to 300.

5. A one-step method of applying a protective coating at roomtemperature, said coating having a thickness greater than 5 mils whichcomprises a single application of a composition composed substantiallyof an aliphatic 40 diamine having the structural formula ance of thecoatings prepared from the above composihaving an P Y equivalent of from140 to 300 to tilt: tion were excellent substance to be protected.

6. The method of claim 5 in which the application is Example 11 byspraying 21.4 ml. of an epoxy resin (ERL-2795 sold by the 7. The methodof curing epoxy resinous materials Bakelite Company) was mixed with 18.6ml. of a fluid which comprises reacting at a temperature at least ashigh fatty aminopropylamine having an iodine number of 89 as roomtemperature, a glycidyl polyether of 2,2-bisand the resulting mixturehad a viscosity of C-D on the Gardner-Holdt scale. This composition wasreadily (p-hydroxy phenyl)propane having an epoxy equivalent of 140 to1000 with an aliphatic diamine having an sprayable through an ordinaryspray gun at room temiodine number greater than and the structuralforperature. After being baked at 300 F. for 15 minutes mula RNI-I-(CHQNH in which R is an aliphatic hypanels coated in this fashion had asmooth, glossy and drocarbon radical having 8 to 22 carbon atoms and xhard coating. is an integer from 1 to 4.

Thus, the combination of this invention are especially 60 8. The methodof claim 7 in which R is derived from valuable solids coatings that showa remarkable fatty acids having an iodine number greater than andchemical and weather resistivity which may be cured less than 200.

at room temperature or by baking. They may be pig- 9. The method ofclaim 7 in which x is 3.

mented in the same fashion as other paints or coatings.

Although it is preferable to use the compositions of this 65 ReferencesCited in the file of this patent inventifn as 180? solljilds; coatingsin certain atpplical; UNITED STATES PATENTS ions 1 may e esira e 0 usevarious so ven s Wl them. Illustrative solvents are xylene, isobutylmethyl Jjuly ketone, benzene, petroleum spirits and the like. It will 70412 gxg z :2 1953 also be recognized that the compositions of this m-2,723,241 De Groote et a1. "w Nov 8, 1955 vention will also be useful asadhesive and laminates.

1. COMPOSITIONS SUITABLE AS PROTECTIVE COATINGS COMPRISING (A) ANALIPHATIC DIAMINE HAVING AN IODINE NUMBER GREATER THAN 75 AND THESTRUCTURAL FORMULA